Design optimization of cruciform specimens for biaxial fatigue loading
Journal Title: Frattura ed Integrità Strutturale - Year 2014, Vol 8, Issue 30
Abstract
In order to correctly assess the biaxial fatigue material properties one must experimentally test different load conditions and stress levels. With the rise of new in-plane biaxial fatigue testing machines, using smaller and more efficient electrical motors, instead of the conventional hydraulic machines, it is necessary to reduce the specimen size and to ensure that the specimen geometry is appropriated for the load capacity installed. At the present time there are no standard specimen’s geometries and the indications on literature how to design an efficient test specimen are insufficient. The main goal of this paper is to present the methodology on how to obtain an optimal cruciform specimen geometry, with thickness reduction in the gauge area, appropriated for fatigue crack initiation, as a function of the base material sheet thickness used to build the specimen. The geometry is optimized for maximum stress using several parameters, ensuring that in the gauge area the stress is uniform and maximum with two limit phase shift loading conditions. Therefore the fatigue damage will always initiate on the center of the specimen, avoiding failure outside this region. Using the Renard Series of preferred numbers for the base material sheet thickness as a reference, the reaming geometry parameters are optimized using a derivative-free methodology, called direct multi search (DMS) method. The final optimal geometry as a function of the base material sheet thickness is proposed, as a guide line for cruciform specimens design, and as a possible contribution for a future standard on in-plane biaxial fatigue tests.
Authors and Affiliations
R. Baptista, L. Reis, I. Guelho, M. Freitas, J. Madeira
Keywords
Related Articles
- EP ID EP126866
- DOI -
- Views 50
- Downloads 0
Resistenza a fatica di strutture in leghe di alluminio: normative a confronto e verifica sperimentale
Le problematiche relative all’utilizzo delle normative nell’ambito della progettazione a fatica di strutture in leghe di alluminio sono state di recente affrontate in numerosi lavori che hanno messo in luce sia le diffic...
Experimental methods for the characterization of fatigue in microstructures
The mechanical fatigue behavior of gold microbeams is analyzed. Dedicated devices have been designed and built able to produce alternate loading on gold specimens; the electrostatic actuation is used as driving for...
A coupled interface-body nonlocal damage model for the analysis of FRP strengthening detachment from cohesive material
In the present work, a new model of the FRP-concrete or masonry interface, which accounts for the coupling occurring between the degradation of the cohesive material and the FRP detachment, is presented; in particular, a...
The strong formulation finite element method:stability and accuracy
The Strong Formulation Finite Element Method (SFEM) is a numerical solution technique forsolving arbitrarily shaped structural systems. This method uses a hybrid scheme given by the DifferentialQuadrature Method (D...
Use of a gray level co-occurrence matrix to characterize duplex stainless steel phases microstructure
Duplex stainless steels are widely used in industry. This is due to their higher strength compared to austenitic steels and to their higher toughness than ferritic steels. They also have good weldability and high resista...